Loose rocker stud

[Texasdoc]

Last week I was on the track. I was pushing pretty hard, not 100%, but more like 80%. On one lap, I was on light throttle in a turn, about to let someone pass when I heard a loud bang, bang, bang. The motor died over a few seconds.

I pulled off to the side of the track. After being towed back to the pits, I opened the valve cover and found the #5 exhaust rocker had jumped off the pushrod. Further disassembly showed that rocker stud had backed out, creating a loose pushrod guide and loose connection between the pushrod and rocker, allowing the rocker to skip off the pushrod. The pushrod was still straight, the pushrod guide still intact, and the rocker only had minimal scratches to the body where it was hitting the #5 intake rocker. The polylock was still locked to the rocker and the rocker to the stud.

I was able to reinstall everything and only missed one track session. Everything worked fine after that. I don't remember what I used on the exhaust stud threads. I know I used ptfe paste on the intake studs since they go into the intake runners, but don't remember what I used on the exhaust side. I think it was blue loctite. I am positive I torqued them as instructed.

Has this happened to anyone else? Any other suggestions on how to prevent this in the future? I'm not sure if a stud girdle would fit under my valve covers. Or do I just add this to my list of things to check every spring when I take it out of winter storage?

[bobcowan]

Yeah, strange stuff happens on the track. I would pull out all the studs and re-install them. Maybe not needed, but it would help me sleep at night.

Do you have a stud girdle? If not, you should consider it.

[Jim Vander Wal]

I'm kinda partial to T&D Shaft Rockers.
Jim

[blykins]

What did you torque to?

[Texasdoc]

As per AFR's instructions - 55 ft/lbs.

I'm tempted to try a stud girdle. I like the shaft rocker systems but $1300-2000 seems kinda steep. I upgraded to the 7/16 diameter studs and I don't twist it above 6000 rpm on my .600 lift cam. So I shouldn't NEED a girdle.

[blykins]

You don’t need a girdle.

It’s possible that you just missed one. Prob will never happen again.

[Texasdoc]

Originally Posted by blykins

Prob will never happen again.

Story of my life with these heads.

[eschaider]

Originally Posted by Jim Vander Wal

I'm kinda partial to T&D Shaft Rockers.
Jim

The shaft mount rocker design and the cost of a broken engine are an interesting comparison. You might want to think of the cost difference between a stud mount system and a shaft mount system (like the T&D system) as insurance (in addition to a performance advantage), sort of like insuring other valuables — a cost but a benefit.

You basically dodged a bullet this time. You may not be as lucky next time.


Ed

[bobcowan]

Originally Posted by Texasdoc

As per AFR's instructions - 55 ft/lbs.

I'm tempted to try a stud girdle. I like the shaft rocker systems but $1300-2000 seems kinda steep. I upgraded to the 7/16 diameter studs and I don't twist it above 6000 rpm on my .600 lift cam. So I shouldn't NEED a girdle.

No, probably don't Need a girdle.

I had trouble keeping the lock nuts in placed. I tried every kind of lock nut on the market, but they still worked loose and caused mayhem. A stud girdle fixed all of that.

[blykins]

There are underlying issues if you need a stud girdle or shaft rockers for a 6000 rpm hydraulic roller.

I’ve got 7000-8000 rpm small blocks with 700 lbs of spring pressure running with neither.

[Texasdoc]

What type of thread locker do you use on the exhaust rocker studs?

[blykins]

None.

Thread sealant on studs that break through. ARP lube and torque to spec on all others.